Document EP1341545 describes an example of such method, in which a mixture of demineralized bone and water is heated to obtain a pasty medium (viscous phase), which is then mixed with demineralized or non-demineralized bone (solid phase) to form a bone gel or bone putty. This method is complex because it first involves a step of preparing the viscous phase, and then there is the addition of the solid phase. The mixing must be carried out in a sterile environment enabling surgical use, which increases the complexity. In addition, this method has disadvantages, such as the bone paste obtained in this manner is generally inhomogeneous since there is discontinuity between the two phases.
Also known, from document US 2007/0202190, is a similar method that uses cortical bone as the raw material. A fraction of the raw material is subjected to heat treatment at less than 100° C. (without reaching, let alone exceeding, a boiling point) and acid treatment to extract gelatin and, after neutralization and drying, to form a mineralized gelatin. Another fraction of this raw material is distilled in the appropriate manner (typically by acid treatment followed by neutralization and drying) to form demineralized bone powder (DBM—Demineralized Bone Matrix). Bone paste obtained by this method is the result of mixing the mineralized gelatin, DBM, and a liquid phase, such that an osteoinductive effect is obtained. Concerns about injectability, typically via syringe, arise with this type of mixture, due to the presence of particles of different composition. Furthermore, as no terminal sterilization process can be applied to the final mixture, the sterility of the product (required for therapeutic use) requires working under sterile conditions, which makes this an expensive and complex method.
In addition, the preservation of osteoinductive proteins of the DBM fraction is a risk factor in terms of health because prions, which are proteins, are not eliminated during preparation and could be transmitted to the recipient patient. This is why the method disclosed by US 2007/0202190, which is complex with sensitive steps, is of limited use in practice.
Document US 2002/0076429 discloses a method consisting of obtaining a pasty medium (viscous phase) from dehydrated gelatin that has been heat treated (for example by autoclaving) in order to both sterilize it and increase its viscosity. The gelatin is then ground under sterile conditions and mixed with osteoconductive and/or osteoinductive product. The complete process involves grinding and mixing the osteoconductive and/or osteoinductive product in a sterile environment, which makes the method both complex and costly. In addition, the obtained product is solid at 37° C., and requires the surgeon to heat the product to soften it prior to implant, which makes the product complex to use.